Control system for container manufacturing device



y 9, 1969 c. LANGEWIS ETAL 3,457,766

common SYSTEM yon CONTAINER MANUFACTURING DEVICE Filed July 17, 1967 2Sheets-Sheet l INVENTORS CORNELiS LANGEWIS A DEAN SMITH MJQ'ZM ATTORNEYJuly 29, 1969 c, L w s ETAL 3,457,766

CONTROL SYSTEM FOR CONTAINER MANUFACTURING DEVICE 2 Sheets-Sheet 2 FiledJuly 1'7. 1967 INVENTORS CORNELIS LANGEWIS A. DEAN SMITH E N R 0? T .1 nY 8 .n9 ii: m5

United States Patent 3,457,766 CONTROL SYSTEM FOR CONTAINERMANUFACTURING DEVICE Cornelis Langewis, Walnut Creek, and Arthur DeanSmith,

also known as A. Dean Smith, San Lorenzo, Califi, assignors to KaiserAluminum & Chemical Corporation, Oakland, Calif., a corporation ofDelaware Filed July 17, 1967, Ser. No. 653,950 Int. Cl. 1321 7/12; B214122/20; Fb 7/00 US. Cl. 72-432 8 Claims ABSTRACT OF THE DISCLOSURE Apunch and die apparatus of the draw and iron type for manufacturingseamless container bodies wherein at least one punch means is attachedto each side of a common actuating or slave piston that is continuouslyreciprocated in alternate directions by a driving piston or yoke, bothof said pistons being located in a common closed fluid circuit andwherein an improved actuating piston control device is incorporated inthe fluid circuit to prevent improper or unbalanced stroking of saidactuating piston. This improved control device includes a valvemechanism which is substantially immediately responsive to anyunbalanced stroking of the actuating or slave piston so as tosimultaneously adjust the fluid pressure on opposing sides of theactuating piston, effect return of the same to the desired preselectedvalues and a balanced stroking of the actuating piston relative to thedriving piston or yoke.

BACKGROUND OF THE INVENTION This invention relates to a draw and ironapparatus for producing seamless container bodies provided with a bottomand a side wall formed integrally therewith More particularly, it isconcerned with P oviding an improved fluid actuating system for such anapparatus wherein precise control of the stroking of a main actuatingand reciprocating piston is effectively maintained at all times duringproduction operations The precise and reliable control of the strokingof the actuating piston is particularly important since at least oneforming ram is attached to each of the opposing sides of the actuatingpiston whereby movement of the actuating piston in either directionconstitutes a working stroke of the piston and at least one containerbody is formed on each working stroke. Further, the machine is adaptedto stroke in each direction at the rate of 120 to 160 times per minute,all of which accentuates the problem of maintaining a uniform andbalanced stroking of the actuating piston in both directions. This samestroking control must occur not only substantially immediately but alsoin a relatively smooth fashion because in a draw and iron operation thewall thicknesses of the container bodies are very small and on theorder, for example, of .006 inch. If excessive jarring of the machineparts occurs during any part of the operation, the entire draw and ironoperation could be seriously adversely aifected.

Various schemes have been proposed in the past, such as that shownparticularly in US. Patent 3,167,044 to H. G. Henrickson, wherein afluid operated device is disclosed for making container bodies by thedraw and iron process and wherein a common actuating piston is employedto the opposite sides of which a separate forming ram is attached. Acrank driven driving piston or yoke located in a common fluid circuitanalogous to that employed herein for continuously driving an actuatingpiston is shown in prior US. Patent 2,766,590 to R. L. Erwin et al. Afluid coupling makeup system is also shown in US. Patent 3,314,274 to C.Langewis. To date, however, prior practices have not advantageouslycombined, in the unique fashion proposed in a draw and iron apparatus, adriving piston or yoke for continuously reciprocating an actuatingpiston to each of the opposite sides of which a forming punch has beenattached together with a reliable stroke control device whereby asubstantially immediate correction of any unbalanced stroking of theactuating piston relative to the driving piston or yoke is provided for.The driving system of the Henrickson patent, which is completelyhydraulic, is relatively slow acting and has the inherent problems offluid leakage. When a main driving piston or yoke of the type shown inthe aforesaid Erwin et al. patent is incoporated in a common fluidcircuit with a common actuating piston of the type shown in theHenrickson patent, additional problems exist in that the continuous andrapid reciprocation of the actuating piston can accentuate unbalancedstroking and any correction must be done as provided in the instantdevice in a substantially immediate, reliable and smooth fashion. Thefluid makeup system of the Langewis patent was not incorporated in acommon fluid system involving a driving yoke for stroking an actuatingpiston in both a forward and backward direction.

SUMMARY OF THE INVENTION Accordingly, it is the primary purpose of theinstant invention to provide an improved container manufacturingapparatus of the draw and iron type wherein the proper stroking of thepunch means attached to each of the opposing sides of a common piston iseflected by reliably and smoothly controlling the stroke of the commonactua ing piston at all times thereby inhibiting under-or over-travel ofthe punches through their associated dies. In effect, the equipment isset at all times to function in a constant self-correcting fashion,

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an abbreviated schematicview of the overall control system for the apparatus shown in HenricksonPatent 3,167,044, reference being made to this system as evidencingprior art concepts in this field;

FIGS. 2 and 2a are schematic views of the fluid actuating and controlsystem of the instant invention used on a double acting draw and ironapparatus; and

FIG. 3 is a sectional view of a poppet valve used in the common fluidcircuit of the instant invention.

As indicated above, a prior art control system over which the instantinvention is an improvement is illustrated in prior US. Patent 3,167,044to H. G. Henrickson. The description of the fluid operating circuit ofthis Henrickson patent will be somewhat brief, but of sufficient detailto indicate the problems involved in such a system and the features andadvantages of the instant system thereover, reference being made to FIG.1 of the drawings.

The Hendrickson device is generally comprised of a housing 2 closed offat each end by appropriate closure members 4. Each of the closuremembers 4 was provided with a central opening 6, which was aligned witha similar opening 8 in the end or cap members 10 for the cylinder barrel12 within which a common actuating piston 14 was mounted. Attached tothe opposing sides of the actuating piston 14 was an elongated pistonrod 16 and the free end of each of the piston rods 16 carried a formingram 13. Each of the forming rams 18 was adapted to be passed throughwhat is commonly referred to as a tool pack 2% which included a seriesof appropriate drawing and ironing dies. The tool pack 20 as indicatedin the patent also contained a bottoming die 22 used to appropriatelyform and dome the bottom of the container body upon the termination ofthe stroke of a forming ram 18 as it finally carried the drawn andironed workpiece or container body through the tool pack 20 and causedit to be exited therefrom. Mounted in one bottoming die was a limitswitch 3LS. The other bottoming die carried limit switch 4LS. Theseswitches were adapted to be contacted by the bottom of the containerbody being formed so as to eflect shifting of the actuating piston 14.The opposing sides of the cylinder barrel 12 were ported at 24 and 26. Afluid line 28 led to port 24 and a fluid line 30 led to port 26. Line 28was connected to the port 32 of a four-way valve 33 and line 30 wasconnected to a port 34 of the same four-way valve 33. This same valvealso contained a port 36 connected to a line 38 leading directly to thepump 40 and a port 42 connected to a line 44 which led directly to thereservoir 46. This fourway valve was controlled by conventional andopposing air-operated valves 48 and 50 which, in turn, were controlledby limit switches 3LS and 4LS disposed in the bottoming die unitsmounted on the rightand left-hand sides of the apparatus.

When an appropiate master switch had been closed in the overallelectro-fluid circuitry, the pump 40 was set to initially cause fluid topass through the line 38. When valve 33 was set in the neutral position,ports 36 and 42 were both connected to bypass line 52 in valve 33. Atthis time, the apparatus would be idling and fluid would pass from thepump 40, through line 38, valve 33 and back to tank 46 through line 44.After valve 33 was actuated by appropriate means (not shown) so as toconnect ports 36 and 32 by valve line 54, fluid passed from the pump 40through line 38, port 36 and line 54 into the line 28 and then to theleft-hand side of the common actuating piston 14 while fluid wassimultaneously evacuated from the opposing side of piston 14 in thecylinder 12 out through port 26, then through line 30, port 34 of valve33 and then through the interior line 56 of valve 33 and port 42 intoline 44 and thence into tank 46. All of this is accomplished byoperating the air valves 48 and 50 in an appropriate manner and asdescribed in said patent. When the system is set for automatic operationas actu-t ating piston 14 ends its stroke to the right, the limit switch4L5 will be tripped to operate the air valve 50 in such a fashion as toput interior valve line 58 in communication with ports 34 and 36 of thevalve 33, while interior line 60 of valve 33 is put in communicationwith ports 32 and 42 of the valve. This causes a shifting of the piston14 in the opposite direction. Simultaneously therewith, of course, airvalve 48 will have been operated as described in the patent to permitthis action to take place. At this time, fluid passes from the pump 40through lines 38, interior line 58 of valve 33 and line 30 into theright hand side of the cylinder 12 while it is being simultaneouslyevacuated from the left-hand side of cylinder 12 through line 28, valve33, interior line 60 and line 44 into reservoir 46 until piston 14completes its left-hand stroke and the bottom of the formed container inthe left-hand tool pack 20 contacts the left-hand bottoming die 22 andoperates limit switch 3LS controlling air valve 48 whereby this valvethen shifts the spool of valve 33 into the position where interior line54 of valve 33 is again connected to the fluid lines 28 and 38 andinterior line 56 is connected to lines 30 and 44. At the same time airvalve 50 is operated to permit shifting of the spool in valve 33. Thisautomatic cycling is continued throughout operation of the apparatusdisclosed in the Hendrickson patent.

From the above description, it will be observed that operation of valve33 is controlled by air-operated valves 48 and 50, and that the lattervalves are controlled by the limit switches 3LS and 4LS located inbottoming dies for the tool pack assemblies 20. The limit switches 3LSand 4LS, because of their location and way of controlling valve 33, arenot substantially immediatley responsive to any improper stroking of thepiston 14. Further, the overall control system of this patent is suchthat corrections in improper stroking are effected simply and primarilyby the pump 40 and do not take place as smoothly or as rapidly aspossible. Rapid correction is necessary in the apparatus of the instantinvention which may be stroking at a rate as high as 160 strokes perminute due to the requirements for exceptionally high speed productionrates. For this reason, the device for self-correcting the stroking ofthe ram must operate immediately and with extreme precision, smoothnessand reliability.

A preferred embodiment of the instant invention as indicated in FIG. 2generally comprises an overall housing 70. Mounted within this housingis a prime mover or power unit 72 comprised of a crank arm shaft 74connected to a pair of crank arms 76, as indicated more particularly inthe right-hand portion of FIG. 2. Crank arms 76 are disposed on opposingstub journals 78 mounted in appropriate bearings and adapted to bedriven by a drive wheel 80 in the conventional fashion. As the drivewheel rotates, it causes movement of the shaft 74 located in a slidefitting 82. At the same time the slide fitting 82 moves up and down inthe hollowed out interior 83 of the double acting yoke 84, it forces theyoke 84 correspondingly to the left or to the right in a cyclic fashionwhereupon the left and right pistons 85 and 86 connected thereto willalso be correspondingly moved forward and backward. As these pistons areforced forward and backward, they will act upon the fluid contained inthe fluid containing chambers 90 and 92 on opposing sides of a commonactuating piston 94 disposed in the hollow interior 71 of an elongatedcylinder 95 located at the top of housing 70. Attached to each of theopposing sides of the actuating piston 94 is an elongated piston rod 96and one or more forming rams 98 suitably connected to the free end ofeach of the piston rods 96. The fluid in chamber 71 and chambers 90 and92 forms a common fluid circuit with piston 94 being disposed in oneportion of the circuit and yoke 84 in another portion of the circuit.These rams 98 are adapted to be passed along With a cup-shaped workpieceto be drawn and ironed through a tool pack 250 made up of various dieelements of the type shown and described in copending application524,637, filed Feb. 2, 1966, now Patent No. 3,399,558, of Langewis etal. and reference may be had to the specification of that applicationfor a detailed showing of such a tool pack.

The chambers 90 and 92 are provided with an overload bypass 99 whichincludes poppet valve assemblies 100 for bringing the baypass intocommunication with chambers 90 and 92. These valve assemblies operate asfollows, reference being made particularly to FIGS. 2 and 3 of thedrawings. Let us assume, for example, that the piston 94 has beenadvanced to the right and some foreign object in the right-hand toolpack acts to obstruct movement of the associated forming ram 98therethrough. When the forward end of the forming ram is obstructed bysuch an object, the fluid pressure in the left-hand fluid chamber 90 andon the left side of the piston 94 is greatly increased therebygenerating a force on the chamfered portion 101 of plunger 101' on theleft-hand valve assembly 100 which is greater than the force of the airpressure in air line 103 which acts to bias the left-hand valve 100 to aclosed position and which can be set, for example, at 28 p.s.i. Air line103 is connected to a bore 200 at the small end of the housing 201 ofthe poppet valve assembly. Air from line 103 passes through chamber 202in valve housing 201 and when the hollow plunger 101 is in the extendedposition shown, the bore 203 in the stem 204 of the plunger communicateswith chamber 205 of housing 201 and allows air to pass freely intochamber 205 so as to keep the plunger 101' of the valve assembly 100 inan extended position. When the fluid pressure in chamber 90 exceeds theair pressure in line 103, the plunger 101' is forced to retract and bore203 then becomes vented to the atmosphere. Plunger 101' remains in thisretracted position until reset by the operator grasping hand knob 206and pushing stem 204 inwardly so that bore 203 in stem 204 againcommunicates with the smaller chamber 202 in the assembly housing 201.

As the left-hand valve assembly 100 opens, fluid in chamber 90 isrelieved by entering bypass 99 and this also forces right-hand valveassembly 100 open to then relieve fluid in chamber 92 in the samefashion as the left-hand valve assembly. Both valve assemblies 100remain open until reset by the operator and allow the fluid in chambers90 and 92 to be in effect released into bypass 99 and circulated backand forth therein instead of in the part of the housing in which piston94 is located. With pressure relieved on piston 94, it will come to astop and remain there until the obstruction has been removed with orwithout the equipment being shut down. The right-hand valve 100 operatesin a similar fashion when an obstruction is placed in the path of aleft-hand forming ram. The use of the bypass for short circuiting of thefluid prevents serious damage to the equipment before it can be shutdown and the ram obstruction removed.

As the common actuating piston 94 moves cyclically to the left andright, at least one ram or punch 98 and a workpiece will be forcedthrough its associated tool pack and effect a drawing and ironing of acup-shaped blank which has been fed by appropriate equipment (not shown)to the tool pack 250 associated with each ram 98. In performing thisdrawing and ironing, a precise and uniform length of stroke of each rammust occur at all times in order to continuously produce container orcan bodies of uniform high quality. When a plurality of rams 98 areattached to each piston rod 96, this problem is seriously aggravated ifunbalanced stroking of the piston 94 occurs in either direction.

Unbalanced stroking of common actuating piston 94 and the resultantoverand understroking of punches 98 are automatically corrected by theimproved control device of the instant invention in the followingmanner.

A pump 110 driven by a motor 110' is used to pump hydraulic fluid, suchas oil, at a low pressure, such as 40 p.s.i., from a tank or reservoir,substantially continuously through the main line 112 and branch line 114to the bearings for the yoke pin 74. Line 112 is further connected tothe leftand right-hand portions of the bearings for the crank arm shaftsegments 78 through the branch line 116, a pressure setting valve 116'and line segments 118 whence the fluid passes to the reservoir or tank.This movement of the oil acts to continuously lubricate all of theaforesaid bearings.

The fluid from the tank is also passed by means of the pump 110 throughthe branch lines 120 and 121 through a series of check valves 122 and124 in line 120 and check valves 123 and 125 in line 121, then to thebottom side of the main fluid compartments 90 and 92 as well as throughthe fluid volume control chambers @126 and 126 interposed in lines 120and 121 intermediate the various check valves 122 and 124, 123 and 125.The respective volume control chambers 126 and 126' are each providedwith an air biased piston .128 which acts against the fluid in each ofthe chambers 126 and 126' and which fluid is held at the above 40 psi.by means of pump 110. Fluid from the lines 120 and 121 in chambers 126and 126' acts to force the pistons 128 to their fully retracted positionin their respective chambers. The piston ends of each of the chambersi126 and 126' are connected to a three-way solenoid operated air valve130, by lines 132 and 133, and valve 130 is further connected to themain compressed air lead-in line 103' by line 135. Fluid lines 121 and120 are further interconnected by means of line segments 136, 137 and138 and line 136 contains oppositely acting check valves 139 and 140.

Operation of valve 130 is controlled at the proper time by means ofmicro-limit switches LS and LS located at opposite sides of theapparatus. One of these switches will be contacted by switch contact Xon a given punch 98 during over-travel thereof resulting from acorresponding unbalanced stroke or over-travel of piston 94 in onedirection and cause the desired shifting of the valve as follows.

If We, for example, assume that the actuating piston 94 hasover-traveled to the left as indicated in FIG. 2 due to a fluid leakagein main chamber 98, micro-limit switch LS will be tripped by theassociated switch contact X on a right-hand punch 98 and an unbalancingof the stroke of piston 94 relative to the stroking of yoke 84. Whenthis happens, reference being made to FIGS. 2 and 2a, limit switch LSwill close-energizing relay R which then closes the contacts R in theline for solenoid 2 and contacts R which establishes a holding circuitfor relay R When solenoid 2 is energized, it immediately shifts thespool in valve 130 whereby ports A and C are connected thereby allowingair from line 135 at a higher pressure than the low pressure of 40 psi.in the hydraulic lines 112, etc., such as at p.s.i., to act againstpiston 128 in volume control chamber 126 to move against the 40 psi.fluid in the chamber 126. This results in forcing substantially all ofthe fluid out of the chamber 126 through line 120 and past valve 124into the bottom of chamber until the fluid loss therein is made up aswell as through line segment 138. The fluid in line 138 then acts toopen valve 140 and allow any excess fluid to then pass valve 140 andmove through exit line 160 at a pressure in excess of the 40 psi. andout through line 112 and into the bearings of the power unit 72 and backto the tank. It is further observed here that during the pumping offluid out of cylinder 126 at an excess pressure, check valves 122 and123 are fluidly biased to a closed position inasmuch as the tanks are atsubstantially zero fluid pressure. As the piston rod of piston 128reaches the end of its stroke, it will contact normally closed limitswitch LS thereby opening this switch and the line leading to relay RWhen relay R drops out, solenoid 2 will be deenergized and the valve 130will return to its neutral position with all ports blocked and with thefluid passing again through line at 40 psi. causing a recession ofpiston 128 in chamber 126 thereby allowing this chamber to be refilledby pump 110 and reestablishing a balance in the overall hydraulicsystem.

Conversely, if there is an over-travel of piston 94 to the right, limitswitch LS will be tripped by a switch contact X on a left-hand punch 98thereby closing this switch. As switch LS closes, it energizes relay Rwhich then closes the contacts R in the holding circuit and contacts Rin the line for the solenoid 1. Movement of solenoid 1 causes a shiftingof the spool in valve 130 whereby ports B and C are connected. Air canthen pass into volume control chamber 126 and effect a movement ofpiston 128 therein and a displacement of fluid out of chamber 126upwardly in line 121 past valve and into the lower part of chamber 92until a full makeup of fluid is obtained therein at the same time excessfluid is exhausted through line 137 to valve 139 causing an opening ofvalve 139 and a dumping of excess fluid through lines 160, 112 foreventual dumping into the bearing exhausts in power unit 72. Similarly,as aforementioned, check valves 122 and 123 are fluidly biased to closedpositions during dumping of excess fluid through lines 160 and 112. Asthe piston 128 in chamber 126 reaches the end of its stroke andevacuates chamber 126, its rod trips switch LS opening this switch andbreaking the circuit to relay R When relay R drops out, it openscontacts R and R thereby deenergizing solenoid 1 and allowing valve toreturn to its inactive or neutral position.

By use of the instant control system, a simple, reliable andinstantaneous operating device is provided for correcting the unbalancedstroking of the actuating piston 94 in either direction so that accuratestroke control of all forming rams 98 on the apparatus is assured at alltimes. The self-correcting stroking of the apparatus takes placeautomatically and smoothly. It insures high quality production of canbodies at all times and allows the attachment of multiple rams to asingle piston rod on each side of the actuating piston 94 so thatseveral container bodies can be simultaneously formed upon the strokingof piston 94 in each direction.

The chambers 71, 9t) and 92, 126 and 126' and bypass 99 are allinitially filled with hydraulic fluid by means of pump 110 and lines 120and 121 prior to operation of the machine. During filling of bypass 99,the poppet valve assemblies 101 are opened by the operator pulling thestem 204 of the plunger 101 outwardly so as to bring the bypass 99 intocommunication with main chambers 90 and 92. Air is bled out of theaforesaid bypass and chambers and the interconnecting piping by suitableair vent valves 260 which have oil drippage leads to the oil reservoir.

An advantageous embodiment of the invention has been shown anddescribed. It is obvious that various changes and modifications may bemade therein without departing from the spirit and scope except asdefined in the appended claims.

What is claimed is:

1. In an apparatus for forming a seamless can body provided with abottom and side wall formed integrally therewith, the combination of aclosed fluid circuit, a piston means mounted in one portion of saidfluid circuit and at least one separate forming punch secured to each ofthe opposing sides of said piston means, means located in anotherportion of said circuit for reciprocating the fluid in said closed fluidcircuit and the said piston means so .as to alternately urge first oneof said punches in a single uninterrupted stroke of the punch through adie means associated therewith and then the other punch in a singleuninterrupted stroke of the punch through the die means associatedtherewith, means for replenishing fluid lost in a selected portion ofthe closed fluid circuit on one side of the piston means, the lost fluidresulting in unbalancing the stroke of the piston means, saidreplenishing means including a fluid containing volume control chamberand means for exhausting the fluid contents of the chamber into saidselected portion of the closed circuit so as to replenish the lost fluidin the said selected portion thereof, and means for actuating saidreplenishing means upon an overstroking of a punch.

2. An .apparatus as set forth in claim 1, including means for openingsaid closed circuit and short circuiting fluid away from said pistonmeans so as to cause stop page of said piston means when passage of apunch through its associated die means is obstructed.

3. An apparatus as set forth in claim 1, including a source of air underpressure connectable to said control chamber, a piston disposed in saidchamber and valve means operative upon an overstroking of a punch forconnecting the source of air under pressure to said control chamber soas to drive the piston therein and exhaust fluid therefrom into saidselected portion of the closed fluid circuit.

4. In an apparatus for forming a seamless can body provided with abottom and a side wall formed integrally therewith, the combination of aclosed fluid circuit means, a piston means mounted in one portion ofsaid fluid circuit means and at least one separate forming punch securedto each of the opposing sides of said piston means, die means associatedwith each punch, means located in another portion of said fluid circuitmeans for reciprocating the fluid in said closed circuit means and saidpiston means so as to alternately move first one punch and then anopposing punch through the respective die means associated with eachpunch, and means including a plurality of makeup fluid containingchambers each of which is connectable to a diiferent selected portion ofsaid closed fluid circuit means for replenishing fluid in a selectedportion of said circuit means upon a fluid loss therein, a pump pistondisposed in each chamber and means including a punch for actuating agiven pump piston to effect an exhausting of the fluid from the chamberfor said pump piston and entrance of the chamber fluid into one of theselected portions of the closed circuit means when an overstroking ofthe said last mentioned punch occurs.

5. An apparatus as set forth in claim 4, including a source of .airunder pressure connectable to said last mentioned chamber and valvemeans operable upon the overstroking of the said last mentioned punchfor connecting said source of air under pressure to said last mentionedchamber and for effecting a driving of the pump piston located therein.

6. In an apparatus for forming a seamless can body provided with abottom and a side wall formed integrally therewith, the combination of aclosed fluid circuit means, an actuating piston mounted in one portionof said fluid circuit means and at least one separate forming punchsecured to each of the opposing sides of said actuating piston, diemeans cooperatively associated with each punch, a yoke means drivinglydisposed in another portion of said fluid circuit means forreciprocating the fluid in said closed circuit means so as toreciprocate said actuating piston and alternately move first one punchand then an opposing punch through their respective die means, and meansincluding a plurality of makeup fluid chambers each of which isconnectable to a different portion of said closed fluid circuit meansfor replenishing lost fluid in given portions of said closed fluidcircuit means, said lost fluid causing an unbalancing in the movementsof the actuating piston relative to movements of the yoke means, a pumppiston disposed in each makeup chamber, a source of air under pressureseparately connectable to each of said chambers, and a valve meansoperable upon the overstroking of a given punch for connecting saidsource of air under pressure to one of said chambers so as to effect adriving of the pump piston therein and an exhausting of the fluidtherefrom into the portion of said closed fluid circuit means whichrequires fluid replenishment.

7. An apparatus as set forth in claim 6, including means for openingsaid closed circuit means and short circuiting fluid away from saidactuating piston so as to cause stoppage of said actuating piston whenpassage of a punch through its associated die means is obstructed.

8. An apparatus as set forth in claim 6 wherein said valve means 'is asolenoid operated valve means and means for actuating said valve meansincluding a switching means that is contacted and operated by anoverstroked punch;

References Cited UNITED STATES PATENTS 2,766,590 10/1956 Erwin 54.53,167,044 1/ 1965 Henrickson 6054.5 3,314,274 4/ 1967 Langewis 723493,353,394 11/1967 Smith 72-347 CHARLES W. LANHAM, Primary Examiner.

G. P. CROSBY, Assistant Examiner US. Cl. X.R. 6054.5; 72347

